Gut bugs Chinese researchers have identified a bacteria which may cause obesity, according to a new paper suggesting diets that alter the presence of microbes in humans could combat the condition.

Researchers in Shanghai found that mice bred to be resistant to obesity even when fed high-fat foods became excessively overweight when injected with a kind of human bacteria and subjected to a rich diet.

The bacterium - known as Enterobacter - had been linked with obesity after being found in high quantities in the gut of a morbidly obese human volunteer, according to the report, written by researchers at Shanghai's Jiaotong University.

The mice were injected with the bacterium for up to 10 weeks as part of the experiment.

The experiments show that the bacterium "may causatively contribute to the development of obesity" in humans, according to the paper published in the peer-reviewed journal of the International Society for Microbial Ecology.

A human patient lost over 30 kilograms in nine weeks after being placed on a diet of "whole grains, traditional Chinese medicinal foods and prebiotics", which reduced the bacterium's presence in the patient's gut to "undetectable" levels, the paper's authors claim.

One of the report's authors, Zhao Liping, lost 20 kilograms in two years after adopting a diet of fermented probiotic foods such as bitter melon to adjust the balance of bacteria in his gut, the American magazine Science said in an article this year on his previous research.

According to the article, Zhao's work on the role of bacteria in obesity is inspired by traditional Chinese beliefs that the gut is the "foundation for human health".

The scientists write in their latest paper that they "hope to identify more such obesity-inducing bacteria from various human populations" in future research.

Professor Andrew Day, a paediatric gastroenterologist at the University of Otago in Christchurch, says the study furthers our understanding of the role of microbes in the development of obesity.

"There is increasing evidence that the flora is an essential part of the development of obesity," says Day.

"It would be way too early to suggest that this should be a more generalised intervention at this stage. However, it raises the possibility that there are other aspects to the flora in obesity and that manipulation in these various other settings may also have potential roles."

Obesity worldwide has more than doubled since 1980, according to the World Health Organisation, with more than 500 million adults worldwide suffering from the condition according to 2008 statistics.